This invention relates to sensors for measuring the strength of applied forces. More particularly, it involves a bi-axial load cell for measuring the rolling resistance of a tire along one axis, and for measuring the test load placed on the tire along a different axis.
It has been commonplace to measure the frictional forces between a tire and a surface as a function of a load placed on the tire, such load representing the weight of a vehicle. In such manner, the tread designs, materials, etc., of the tire can be designed to exactly match the expected load range of the vehicle on which it is to be used. Typically, the load to be placed on the tire may run as high as 4,000 lbs. Due to such high load factors, the prior art method of measuring the frictional engagement of the tire with respect to the surface on which it rides, commonly referred to as the rolling resistance of the tire, employed a plurality of load cells. The tire was coupled to the middle portions of a shaft and both ends of the shaft were rotatably mounted in its own load cell. In other words, the prior art method necessitated the use of two load cells placed on either side of the tire to measure the rolling resistance of the tire as a function of a vertically placed load on the tire. Unfortunately, not only does the use of this two load cell arrangement tend to be costly, the electronics needed to match the two devices in order to get a meaningful reading also needs to be relatively sophisticated.